CHAPTER XXVIII 

 CONTROLLING INSECTS 



It is almost impossible to exterminate completely any kind 

 of insect, so that our fight against them must be with the in- 

 tention of holding them in check. There are four principal 

 methods of doing this. Two of them are Nature's ways and 

 two are means devised by man. 



L Parasitic Enemies. — As was just mentioned in the last 

 chapter, there are many insects which get all their subsistence 

 from other insects. It is often noticed that the Hessian fly is 

 quite troublesome for two or three years and then is not seen 

 again for several years. This is due to the attack of its para- 

 site which increases in such numbers that nearly all the Hes- 

 sian flies are killed. Then the parasite, having nothing to 

 live on, dies off and the Hessian fly has a chance to increase 

 again. In a similar way many other insects are held in 

 check. Besides the parasitic insects there are those like the 

 lady-bird beetle and many others which attack and destroy 

 destructive insects. 



2. Birds, Snakes, and Toads. — Some of Nature's most 

 effective agents in destroying insects are not fully appreciated 

 by man. Almost every kind of bird destroys some insects, 

 and a majority of our land birds live almost entirely on in- 

 sects, especially during the growing season. Certainly every 

 one has seen the robins, chipping sparrows, bluebirds, black- 



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